Polyester molding composition containing aqueous-alkaliextracted-douglas fir bark fiber as a reinforcing agent



United States Patent O POLYESTER MOLDING COMPOSITION CONTAIN- IYGAQUEOUS-ALKALI-EXTRACTED-DGUGLAS FIR BARK FIBER AS A REINFORCENG AGENTArthur 5. Gregory, Tacoma, and Keith D. Gehr and Thomas R, Frost,Longview, Wash, assignors to Weyerhaeuser Company, Tacoma, Wash, :1corporation of Washington No Drawing. Continuation of abandonedapplication Ser. No. 243,630, Dec. 19, 1962. This application Sept. 8,1966, Ser. No. 578,103

Claims. (Cl. 260-174) ABSTRACT OF THE DISCLOSURE A thermosettingcomposition consisting essentially of unsaturated polyester base resin,an unsaturated crosslinking monomer therefor, a reinforcing agentcomprising an aqueous alkali extracted Douglas fir bark fiber andsupplemental filler.

This application is a continuation of SN. 243,630 filed Dec. 10, 1962,and now abandoned.

This invention relates to plastics. It pertains particularly to resinousmixtures useful as molding compositions and comprising a polyester resinand tree bark fiber.

Polyester resinous compositions used for molding and containingconventional reinforcing materials such as glass or sisal have severaldisadvantages.

Thus when glass fiber is used as the reinforcing material, compoundingtime must be held to a minimum to avoid excessive fiber breakage andresulting loss of strength. However, curtailing the compounding timeresults in unequal dispersion of the fiber, and hence in nonuniformmolded product properties. Moreover, when medium or high glass fibercontent is used, the finished molded article will often exhibit roughsurfaces caused by flow patterns of the resin-glass fiber mixture formedduring molding.

Similarly, the inclusion of sisal fiber in polyester resin moldingcompositions creates a defiashing problem because of its toughness andlength. As a result, it is not unusual for a one-man press to demand athreeman defiashing crew. Where medium or high glass fiber content isused, a similar defiashing problem exists.

Further, when either glass fiber or sisal is used as a reinforcingmaterial, a lowering of strength occurs at the weld and kiln lines ofthe molded article.

Still further, polyester resin compositions containing conventionalreinforcing materials because of their soft and tacky properties are notsuitable for application in automatic molding procedures.

Accordingly, it is the general object of the present invention toprovide a polyester resinous composition particularly suitable for useas a molding compound and characterized by the following advantages:

(1) Non-critical mixing.

(2) Adaptability to automatic molding techniques in both compression andtransfer molding equipment.

(3) Easy defiashing.

(4) Relative freedom from warping.

(5) Improved strength at weld and knit lines.

(6) Reduced specific gravity, resulting in increased unit production perpound of molding compound.

(7) Superior appearance and surface qualities including various colors.

It is the fundamental concept of the present invention that theforegoing objects and advantages may be achieved by including as amaterial in polyester resinous composiice tions the fiber content of thebark of trees. Such a fiber content is found in the barks of variousconiferous tree species including redwood, cypress, juniper, the cedarsand, particularly, the Douglas fir.

It is an object of this invention to provide a polyester resinousmolding composition including as a reinforcing material coniferous barkfibers having a particle size so as to pass through a 28 mesh screen andbe retained on a 200 mesh screen and having an average length to breadthratio of :1.

The fiber content of the bark may be separated from the other barkcomponents by either mechanical or chemical procedures. In a typicalmechanical procedure, the bark is ground or milled to a suitableparticle size and is then fractionated mechanically by screening,winnowing or otherwise to obtain the fiber fraction. Where the fiber isobtained from species such as redwood or cedar it is then necessary toreduce the fiber length by cutting or chopping.

A preferred bark fiber is that obtained from the Douglas fir which occurin the form of strong, hard, tough needles which generally are spindleshaped (generally cylindrical with tapering ends) and have a lengthaveraging about 1 mm.

However, these Douglas fir bark fibers are so intimately commingled withthe other bark components that a pure bark fiber fraction is moredifficult to achieve by mechanical means of separation than is the casewith other coniferous barks having fiber.

Furthermore, the non-fibrous components of Douglas fir bark contain ahigh percentage of complex acids and phenolic bodies which act toinhibit the cure of peroxidecatalyzed polyester resins used in thepresent invention.

Accordingly, when Douglas fir bark fibers are used it is preferred toemploy a fiber fraction which has been treated or extracted with anaqueous alkaline treating agent. In preparing such a bark fiberfraction, the whole bark, or a previously separated fiber-containingfraction of whole bark, is reduced by grinding or milling to a particlesize suitable for subsequent processing, i.e., to a particle size volumeof Mt inch cube or less.

The bark is subjected to a chemical treatment in which it is reactedwith an aqueous alkaline treating agent broadly comprising a basicacting compound of an alkali metal or ammonium hydroxide. Caustic sodais a preferred treating agent although other alkaline agents such ascaustic potash, sodium carbonate, sodium bicarbonate, borax and ammoniumhydroxide also may be used.

The bark is treated with the alkaline material in either single ormutliple stages, either batchwise or continuously, with an alkali usageof .from 525%, and at a consistency of the bark of from 5-40%.Appropriate amounts of water are used to produce these conditions. Thetreating time is variable, although in general a period of from 30-180minutes is adequate at a temperature in the range of ambient to theboiling point.

The foregoing treatment serves several important functions. First, andmost significantly for the present purpose, it provides a bark fiberfraction having an alkali soluble content of below 30%, preferably about15%, by weight, dry basis, whereas the whole bark or fiber-containingfraction thereof may have an alkali soluble content of as much asFurthermore, this result is accompanied by dissolution of a substantialproportion of the nonfibrous bark substance from the individual fibers,leaving them as a solid residue.

After the chemical treatment has been completed, the resulting alkalineslurry is withdrawn from the reactor and separated by screening, orotherwise, into an extract fraction and a residual bark fiber fraction.The latter may be washed with hot water or other solvent after which itis applicable directly after drying to predetermined moisture levels inthe formulation of the herein described molding compositions.

However, for some molding compound applications, it may be desirable todry the fiber product to a moisture content of less than 50% by weightand subject it to a screening to remove any wood splinters that may haveadhered to the bark upon removal from the log. It may also be desirable,in some instances, to screen the bark fiber product to free it of anyalkali-insoluble particles of parenchyma or cork cells remaining asdust. All of these are termed herein extracted bark fiber.

Where mechanical means have been used to separate out and provide afiber fraction from Douglas fir bark which is not sufliciently free ofcure inhibiting nonfibrous bark components, the fraction neverthelesscan be used by subjecting it first to a chemical treatment with anaqueous alkali treating agent which reacts sufficiently with the complexacids and phenolic bodies of the nonfibrous bark components to renderthem ineffective as inhibitors to the curing of the polyester resin.These fibers are termed herein chemically treated fibers.

For use in the presently described compositions, the tree bark fiberpreferably first is dried to a final moisture content of from 445% byweight, dry fiber basis. Most of this moisture is retained in the fibersand is not lost during the ensuing molding operation but is retained inthe molded product. When introduced via the fiber, it has theadvantageous effect of increasing the flowability of the composition inthe mold. It also increases the impact strength of the molded productand increases the resistance of the molded product to crazing. However,if the moisture content of the fiber is much above 15% problems ofblowing and blistering are encountered duriug molding.

The polyester resin which is used together with the tree bark fiber asan essential component of the herein described compositions broadlycomprises the resinous product produced by the copolymerization of apolyester base resin and an unsaturated cross-linking monomer therefor.The polyester base resin is usually sold dissolved in the crosslinkingmonomer with a typical composition being 6075% polyester and 40-25%monomer.

The polyester base resins are articles of commerce characterized aspolymerizable, olefinically unsaturated, polyhydricalcohol-polycarboxylic acid polyesters. Such esters are produced by thecopolymerization in known manner of a polyhydric alcohol, a saturatedpolycarboxylic acid and an unsaturated polycarboxylic acid.

Examples of polyhydric alcohols which may be employed as components ofthe polyester base resins are ethylene glycol, propylene glycol, the1,2-, 1,3-, and 1,4- butane diols, the 1,2-, 1,3-, 1,4-, and 1,5-pentanediols, 1,6-hexane diol and the like. Ethylene glycol and propyleneglycol are of particular interest for the present purpose.

Examples of saturated polycarboxylic acids which are useful'ascomponents of the presently described polyester base resins are thosewhich are free of nonbenzenoid unsaturation, including the saturatedaliphatic polycarboxylic acids such as malonic, succinic, glutaric,adipic, pimelic, suberic, azelaic, and sebacic, as well as the henzenedicarboxylic acids such as phth-alic acid, :benzoyl phthalic acid,isophthalic acid, terephthalic acid and the chlorinated phthalic acidssuch as tetrachlorophthalic acid. Whenever available, the anhydrides ofthese acids,

or mixtures of these acids and their anhydrides may be employed. Of theforegoing group phthalic anhydride,

isophthalic acid and terephthalic acid are particularly suitable for thepresent application.

Examples of unsaturated polycarboxylic acids which may be included ascomponents of the herein described polyester base resin are the alphaethylenically unsaturated alpha beta dicarboxylic acids such as maleicacid. Here again the anhydrides of the acids may be employed wheneverthey are available, either alone or in admixture 4 with the free acids.Maleic anhydride and fum-aric acid are particularly suitable.

The unsaturated cross-linking monomer which is employed together withthe above described polyester base resin in producing the finalcross-linked copolymer comprises broadly a copolymerizing vinylderivative such as styrene, vinyl toluene, and diallyl phthalate. Theside chain-substituted styrenes such as alpha methyl styrene, alphaethyl styrene and the like also may be used. Still further, there may beemployed the ring-substituted styrenes such as the ortho, meta andparaalkyl styrene, 2,4-dimethyl styrene, 2,5-diethyl styrene and thelike. Of the foregoing, styrene, vinyl toluene and diallyl phthalate arepreferred cross-linking monomers for the present purposes.

When an unsaturated polyester base resin and an unsaturatedcross-linking monomer therefor are mixed in the desired proportions andheated, copolymerization by addition reaction takes place between theunsaturated linkages of the two components to form as the final producta cross-linked thermoset polymer. The most common method of triggeringthis copolymerization is by the use of catalysts or initiators whichpreferably are of the organic peroxide type.

Particularly suitable organic peroxides to be used for this purpose arebenzoyl peroxide, and, where longer resin shelf life is required,tertiary butyl perbenzoate. Other examples of suitable organic peroxidecatalysts are cumene hydroperoxide, methyl ethyl ketone peroxide,tertiary butyl peroxide, and the like.

These and other catalysts decompose upon heating into highly active freeradicals that initiate the free radical reactions necessary for thecopolymerization. They may be included in the molding compositions inrelatively minor proportions, i.e. in proportions of from Gill-3% byweight, based on the total weight of the composition.

In addition, to present premature reaction of the unsaturated polyesterbase resin, an inhibitor usually is included in the uncured resinousmixture. This usually is included in the polyester resin base at thetime of manufacture. Occasionally, however, the compounder will addadditional inhibitor during compounding to give other propertiesincluding additional stability and hence longer shelf life to themixture.

The preferred inhibitor is hydroquinone, although other inhibitors maybe used including ditertiary-butylhydroquinone, benzaldehyde, ascorbicacid, resorcinol, etc.

These are used in small but effective proportions, i.e., in v aproportion of from 0.0l-0.5% by weight of the molding composition.

If desired, various supplementary mineral or organic fillers may beincluded in the compositions of the invention together with the treebark fiber and polyester resin. There may be employed semi-reinforcingmineral fibers such as wollastonite, and particularly, asbestos. Theseimpart to the mix better molding properties and increase the ilexuraland impact strength of the molded product.

Asbestos is a preferred semi-reinforcing mineral filler for use with thetree bark fiber. The tree bark fiber, in addition to supplying strengthas a reinforcing fiber, because of low oil absorption properties,offsets the high resin demand normally accompanying the use of asbestosfiller. Hence the two materials complement each other in theirproperties. Also, the asbestos filler reduces to a very high degree theshrinkage factor of the molded products and prevent the development ofthermal strains in them.

Still other exemplary mineral 'or inorganic fillers which may beemployed in the instant compositions are the kaolinite clays, calciumcarbonate, talc, calcium sulfate, baiytes, etc.

To develop particular properties in the molded products it ispermissible to include in the molding compositions suitable proportionsof such materials as glass fiber, sisal fiber, cotton flock and thelike.

In addition to the various types of fillers outlined above, still othersupplemental materials may be used to impart desired properties to themolding compositions and molded products.

For example, there may be included a minor proportion by weight of thetotal compositon, of a suitable mold release compound such as stearicacid, zinc stearate, or lecithin.

Suitable organic solvents such as the lower aliphatic alcohols andketones, particularly methyl-ethyl ketone, also may be included in smallquantities to improve the degree of dispersion of the ingredients.

Where desirable, various pigments and dyes may be included in suitableamounts.

The foregoing materials may be used over a wide range of proportions,depending upon the identity of the components of the resinous mixturesand the properties it is desired to develop therein. In general, asufiicient amount of the unsturated cross-linking monomer is employed toreact efficiently with the unsaturated polyester base resin. Asufiicient proportion of the tree bark fiber and of the supplementalmineral or organic fillers is employed to provide the necessary bulk andproduct qualities and to conribute necessary strength to the moldedproduct. The relative proportions of these three primary ingredients ofthe compositions are shown below, expressed in percent by weight of thetotal resinous composition:

The proportions of the secondary constituents of the compositionslikewise are Widely variable depending upon their identity and theproperties to be imparted to the mixtures. Thus suficient of theperoxide or other catalyst is employed to polymerize the resin at areasonable rate. In a typical case, this amount is from 0.1 to 3% byweight, based on the total resinous composition.

Similarly, a sufiicient amount of the hydroquinone or other inhibitor isadded, either during manufacture of the base resin or duringcompounding, to stabilize the composiiton against premature gelation andto give it the desired shelf life. In a typical instance this amount isfrom 0.01 to 0.5% by weight, based on the total weight of the resinousmixture.

Suficient mold release compound is used to insure clean and easy releaseof the molded article from the mold. In most instances this amount willvary from 0.1 to 3% by weight, based on the total weight of the mixture.

In cases where an organic solvent is employed to disperse theconstituents, a quantity of from 0.01 to 2% by Weight, based on thetotal weight of the mixture, usually is suitable.

A specific formulation adaptable for use with ditlerent types ofpolyester resin is as follows, the proportions being given in percent byweight of the total resinous composition:

The herein described resinous compositions may be mixed and compoundedusing any suitable technique which will secure uniform dispersion of theconstituents throughout the mix.

In a typical procedure, the benzoyl peroxide or other catalyst first isadded to additional cross-linking monomer, if used, and this solution isadded to the polyester resin. Otherwise the catalyst can usually beadded directly to the resin.

The hydroquinone or other inhibitor, if used, is dissolved in anappropriate quantity of methyl ethyl ketone or other organic solvent.This solution then is added directly to the polyester resin.

The tree bark fiber is placed in a mixer and blended with the catalyzedresin prepared as outlined above. The asbestos filler is added to themixture and the mixing procedure continued until dispersion of theconstituents is complete. The mixing time cycle in a typical case is but3-4 minutes using a high shear mixer, but may require 20-45 minutes in adouble arm kneader type mixer. This moldin composition mixture then maybe molded in matched metal dies at pressures of the order of 400-1000psi. and temperatures of the order of 250-350" F., using cure times offrom 30-90 seconds or longer depending on section thickness. As notedabove, the molded pro-ducts are Very easily defiashed and show a reducedtendency to Warp during cooling.

The resinous compositions of the invention are illustrated further inthe following examples:

Example 1 This example illustrates a typical procedure for preparing amechanically separated tree bark friction for use in the compositions ofthe invention.

Douglas fir bark was milled in a hammermill provided with inch screenand dried to a moisture content of about 15%. The ground bark materialwas placed on a double deck vibrating screen, the top screen of whichwas 14 mesh (Tyler Standard) and the bottom 88 mesh (Tyler Standard).The parenchyma powder fraction passed both screens. The fiber fractionwas retained on the second screen.

The fiber fraction was passed to a ball mill to further disengagenon-fibrous bark substances from the fiber and then screened on avibrating screen to separate out a fiber fraction which passed through a34 mesh screen and was retained on a 88 mesh screen (Tyler Standard).This fiber fraction was ground in a high speed hammermill having a 7-3inch mesh opening screen and then passed through an air separator. Thecoarse fraction from the air separator was then screened and thefraction passing through an mesh screen but retained on a mesh screen(Tyler Standard) was used as the tree bark fiber in a polyester resinmolding composition.

Example 2 This example illustrates a typical procedure for preparing achemically treated bark fiber used'in the resinous compositions of theinvention.

Douglas fir bark was ground, ball milled, and screened as in Example 1.However, the fractions passing through the 88 mesh screens were combinedand passed through the same sequence of steps of hammermilling, airseparation and screening. To the fraction passing the 80 mesh screen andremaining on the 150 mesh screen (Tyler Standard) was added sufiicientsodium hydroxide and water to enable the mixture to be stirred and toraise the pH of the mixture at equilibrium to 8.3. At such time thewater was drained off and the fiber dried to a moisture content of 7%.This reaction with caustic was sufiicient to render ineffective theinhibiting feature of the complex acids and phenolic bodies of thenon-fibrous bark components which were present in greater proportionthan in Example 1 because of the fine 88 mesh screen particle size ofthe base material.

Example 3 Benzoyl peroxide catalyst 8.80 1 This example illustrates atypical procedure for pre- Hydroqumone mhlbltor Zinc stearate moldrelease compound 9.6 paring the extracted bark fiber used in theresinous com- Meth 1 eth 1 ketone or anic solvert 1 10 positions of theinvention. y y g 1 DQ110133 fir bark wa d d t a ti l i a hammer. 1Plaskon 9520 This is believed to be a condensation a product of ethyleneglycol, phthalic anhydride, and maleic mill have /16 inch screen. Theground bark was treated acid dissolved in vinyl toluene. in a continuouscountercurrent two-stage extraction systern with the bark fed into thefirst stage and an aqueous Preparatory to formulating, the solid benzoylperoxide caustic soda solution having a concentration of 50% by catalystgranules Wereadded to the y n a o y weight fed'together withcountercui-rerit wash liquor into to soak for about 5 minutes. Thehydroquinone inhibitor the econd tage The tempe aiufg maintained in thee was (llSSOlVed in 5 times its Weight Of methyl ethyl ketone. tractiony tem wa ab t; 200 F, Th pH values were This in turn was dissolvedcompletely in the unsaturated 10 in the first stage and 13 in the secondstage, while the p ly r sin- T e benaoyl peroxide-styrene slurry wasconsistencies were 8% and 7% respectively, and the dwell then added t thmhl lted e m base solutlon and the ti were 60 i t i h Stage mixturestirred until solution of the benzoyl peroxide was A caustic sodaextract product of the bark was produced complete. continuously from thefirst stage and a treated extracted NeXt, the y Constltllents of t30111190510011, the bark fiber product was produced continuously fromthe bark fiber, t abestos and the ZIBC Steafate, were Placed secondstage, Th b rk fibe product was passed over a in a high shear mixer andblended 30 seconds. The catavibrating screen separator onto a washinghorizontal lyled resin Solutlon Was added, with the miXeI' running,vacuum pan filter and then through a roll press. The over a 35-40 secondperiod. Mixing was continued for a pressed product then was dried to amoisture content of total of 3 minutes. 7% by weight in a rotary drumdrier, heated to 450 F. The completed premix was withdrawn from themixer at the inlet. r and molded into test panels in 60 seconds at 270F. The It was suitable per se for use in the resinous molding 20 testspecimens then were subjected to standard tests with compositions of theinvention. However, as mentioned results as follows:

Example Flexural Strength, p.s.i 7, 000 8, 430 7, 770 9, 670 7, 820 7,360 Flexural Modulus, .s.i.Xl0- 8.0 10.9 8.46 11.8 10.0 9.25 IzodImpact, ft. lb inch of notch 2.0-215 0.57 0.72 0 .75 0.80 0.50 DroppedBall Impact, inches- 2G-37 13-18 15-21 20-23 2029 15-19 BarcolHardness--- 37 43 35 32 Cure Time, seconds 23 25 22 24 23 Flow, inches11%; 9 10 46 10 8 7 1 These are average properties of a. typical 10%sisal-polyester resin molding composition.

2 41 grams of molding composition is molded into a disc 4 inches indiameter and V thick for 60 seconds at 270 F. and 800 p.s.i. A poundball impact head is dropped on the disc from heights increasing inincrements of 1 inch. The first figure report is when failure occurs.

a A molding composition preform, 2 x 4 x the height when a crack firstappears, and the second figure is the height weighing 140 grams, isplaced crosswise at the step end of a 6 x 12' die having a step, 3% longat one end and is molded for 60 seconds at 270 F. and 655 p.s.i. Thedistance the compound moves down the die before curing is reported ininches.

previously, where desirable, subsequent screenings can be made to insurecomplete removal of any wood splinters or dust particles.

Example 4 In a manner similar to the foregoing, alkali treated barkfiber from cedar was prepared. However, after obtaining the extractedfiber it was necessary to reduce the particle size in a rotary cuttingmill and by screening to obtain the 80 +150 mesh size suitable for usein the molding compositions of this invention.

Example 5 Example 6 The above examples of coniferous tree bark fiberswere compounded in a typical molding composition of the invention usinga polyester resin. The compositions had the following formulation:

. Grams Polyester resin 1 -11."- 406 Styrene monomer 32.4 V Coniferoustree bark fiber 432 Asbestos filler 600 Example 7 The procedure ofExample 6 was followed, but using extracted Douglas fir fiber anddifferent polyester resins in the following formulation:

Percent by Weight The first polyester base resin used in the aboveformulation was Plaskon Pe-l80. This is believed to be a condensationproduct of ethylene glycol, ortho-phthalic acid or anhydride and maleicand/or fumaric acid dissolved in vinyl toluene.

The second polyester base resin used in the above formulation was Stypol2214. This is believed to be a condensation product of ethylene glycol,sebacic acid and maleic acid dissolved in vinyl toluene.

The third polyester base resin used in the above formulation wasReichhold DD-247. This is believed to be a condensation product ofethylene glycol, isophthalic and sebacic acid and maleic anhydridedissolved in styrene.

The mixed compositions were molded and the molded products subjected tostandard tests with results as follows:

This example illustrates the strength knit lines provided by thereinforcing bark fibers of this invention. Molding composition A and 3of Example 6 each were molded into 6 X 12 sheets with half of the chargeplaced at each end of the die. Flexural strength test specimens were cutfrom the sound area on either side of the knit line and in the knitline. The results were as follows:

Crosswise Flexural Strength, p.s.i 6, 200 7, 170 Knit: Line FlexurmStrength, p.s.i 4, 100 5, 720 Percent Reduction 34 20 From the foregoingdescription and examples it is seen that the present invention by usingthe bark fiber of coniferous trees as a reinforcing fiber for polyesterresin molding compositions produces molded articles of equivalentutility to those heretofore produced by the use of sisal without thedisadvantages associated with such use. The particle size of 28+200 meshfor the bark fiber as compared to the /2 inch length commonly used inchopped sisal, and the strong, hard, tough characteristics of thesefibers all contribute to provide the advantages of easier defiashing,stronger knit lines, good flow and less tendency to warp compared tothose polyester molding compositions previously known. The resistance ofbark fibers to resin absorption permits a higher usage and a drier andfirmer premix which is adaptable to transfer molding. Thus, usages ofbark fiber can range from 60% with a preferred range being 15-35%resinous mixture whereas sisal is seldom used in amounts above 10%because of deleterious effects on flow and mixing.

Having thus described our invention in preferred embodiments, we claimas new and desire to protect by Letters Patent:

1. A thermosetting composition comprising a catalyzed, thermosetting,polymerizable, olefinically unsaturated, polyhydn'calcohol-polycarboxylic acid polyester base resin; an unsaturatedcross-linking monomer therefor; a reinforcing agent comprising anaqueous-alkali-extracted Douglas fir bark fiber having a residualaqueousalkali-soluble content of not over 30% by weight, dry

solids basis, and an inorganic supplemental filler, used in thefollowing proportions:

Percent by weight Polyester base resin and cross-linking monomer 20-80Douglas fir bark fiber 10-60 Supplemental filler 2-70 2. A thermosettingcomposition comprising a catalyzed, thermosetting, polymerizable,olefinically unsaturated, polyhydric alcohol-polycarboxylic acidpolyester base resin; an unsaturated cross-linking monomer therefor; areinforcing agent comprising an aqueous-alkaliextracted Douglas fir barkbast fiber having a residual aqueous-alkali-soluble content of not over30% by weight, dry solids basis and an inorganic supplemental filler,used in the following proportions:

Percent by weight Polyester base resin and cross-linking monomer 20-40Douglas fir bark fiber 15-35 Supplemental filler 35-45 3. Thethermosetting composition of claim 2 wherein the Douglas fir bark fiberhas a moisture content of from 415% by weight, dry bark fiber basis.

4. The thermosetting composition of claim 2 wherein the inorganic fillercomprises an asbestos filler.

5. A thermoset'ting composition including aqueousalkali-extractedDouglas fir bark bast fiber having a residual aqueous-alkali-solublecontent of not over 30% by Weight, dry solids basis, the compositionincluding the following constituents employed in the indicatedproportions:

Percent by weight r Polymerizable, olefinically unsaturated polyhydricalcohol-polycarboxylic acid polyester resin 25-35 Additionalcross-linking monomer 0-5.0 Douglas fir bark fiber 15-35 Asbestos filler35-45 Peroxide catalyst 0.1-3

Inhibitor 0.0l0.5

Mold release compound 0.1-3 Organic solvent 0-2 References Cited UNITEDSTATES PATENTS 2,697,081 12/1954 Heritage 260-172 2,852,487 9/1958 Maker260-9 2,890,231 6/1959 Heritage of a1. 260-4125 2,985,615 5/1961Tunteler et al 260-9 3,023,136 2/1962 Himmelheber 260-173 r WILLIAM H.SHORT, Primary Examiner. 0

JAMES A. SEIDLECK, Examiner.

E. M. WOODBERRY, I. NORRIS,

Assistant Examiners.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No.3,361,690 January 2, 1968 Arthur S. Gregory et a1.

It is hereby certified that error appears in the above numbered patentrequiring correction and that the said Letters Patent should read ascorrected below.

Column 1, line 50, for "kiln" read knit column 4, line 37, for "present"read prevent column 5, line 19, for "unsturated" read unsaturated line24, for "con'ribute" read contribute line 50, for "composiition" readcomposition column 6, line 33, for "friction" read fraction column 7,line 6, for "have" read having columns 7 and 8 sub-headings to the tablefor "A l 3 3 4 5" read A l 2 3 4 S same table fifth column, line 8thereof, for "10 14/16" read 9 14/16 column 8, line 53, for "monmer"read monomer column 9, first table, third column, line 5 thereof, for"19 22" read 19-22 Signed and sealed this 15th day of April 1969.

(SEAL) Attest:

EDWARD M.FLETCHER,JR. EDWARD J. BRENNER Attesting Officer Commissionerof Patents

